(CNN) -- On the one side is business, the economy and growth. On the other is the environment, a village and thousands of local residents. Now that the British government has published consultation this week for a third runway and sixth terminal at London Heathrow Airport, the debate can begin.

Local campaigners say two million residents will be affected by noise pollution from a third runway.

The proposition is for a 2,200 meter runway to be built north of Heathrow by 2020. This would almost double the number of passengers passing through one of the world's largest airports and increase the number of flights from 470,000 to 700,000 a year.

This week, Transport Secretary, Ruth Kelly insisted the expansion of one of the world's largest airports was necessary to boost the economy. "Heathrow supports 170,000 jobs, billions of pounds of British exports and is our main gateway to the global economy. But for too long it has operated at nearly full capacity, with relatively minor problems causing severe delays to passengers," Kelly said.

Heathrow currently operates at 99 percent capacity. With no give in the system, any sign of bad weather and operations rapidly fall apart.

"If nothing changes," Kelly said, "Heathrow's status as a world-class airport will be gradually eroded -- jobs will be lost and the economy will suffer."

This week British Airways and Virgin Atlantic put their weight behind airport expansion. As BA CEO Willie Walsh told CNN, Heathrow was losing its status as a leading global airport. In terms of the number of destinations served, Heathrow has fallen to number five in the league, Compared to Heathrow's two runways, Schipol in Amsterdam has five, Paris four and Frankfurt three.

"This is a serious wake-up call," says Walsh. "London is the business capital of the world and if we want to maintain that position we have got to have proper infrastructure."

A new airport is not an option, said Steve Ridgway, Virgin Atlantic's CEO. "The economic and environmental impact of starting again and putting in the links would be far greater than is being proposed at Heathrow," he says.

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A more efficient airport would benefit customers, he added. "It is not a good experience going through an airport that is 99 per cent full," he says. More carriers serving a larger airport will also spur competition for airlines. For travelers this will mean better service, products and good fares, says Ridgway.

Greenpeace disagree. They say the only reason for a third runway is to increase the profits of the BAA and the major airlines. Documents the environmental group obtained under the Freedom of Information Act demonstrate a close cooperation between BAA and the Department for Transport (DfT) in preparation of the consultation.

The public has until February 27 to comment on the expansion proposals in the consultation. There is expected to be a torrent of negative reaction.

Greenpeace has estimated that a 70 percent increase in flight numbers and the resulting rise in climate change pollution will be equivalent to the entire annual emissions of Kenya.

Ken Livingston, Mayor of London is opposed to the scheme despite the government's assertions that expansion will boost the city's economy. Conservative London mayoral candidate, Boris Johnson, and the Liberal Democrats have also expressed opposition for environmental reasons.

Part of the proposal under consultation is to introduce "mixed-mode" use of existing runways as an interim measure so they can handle both take-offs and landings. At the moment the two runways are used for either take off or landing at any one time. This arrangement was designed to give residents some respite from the sound of overhead aircraft.

Airlines say mixed-mode will dramatically increase the efficiency of the airport. BA also argues that the current stacking system -- where up to eight planes can queue in four stacks over the airport -- uses up more fuel and increases carbon emissions.

Further development at Heathrow is conditional. say the DfT, on "strict local noise and air quality limits". And as Walsh told CNN, the airline industry also needs to steps up to meet these.

"We are investing billions of dollars in new aircraft that are quieter and more fuel efficient. Airlines have to recognize there is an environmental impact and play their part. Part of that going forward will be the inclusion of aviation in the European Emissions Trading Scheme from 2011."

Whether the critics agree with this, or think this is enough to combat the effect of flying on climate change is another matter.

The closing date for responses to the consultation is 27 February 2008. The DfT is staging a series of public exhibitions in communities around Heathrow during the consultation period. Final policy decisions will be taken in 2008.